I began a presentation using a general template. After adding a pdf to one of the slides, I double-clicked on the page and the aspect ratio of the whole thing stretched and circles are elliptical and the squares are rectangles, etc. I have no idea how to make it go back. I open a previous presentation and it also has stretched.
How do I get it back to a normal display? I am on a 27 inch iMac, and so the aspect ratio of the screen is 16:9.